Stuck-osaurus: Mass grave unearthed of young dinosaurs who died 90million years ago after getting trapped in the mud

Scientists have unearthed a mass grave of young dinosaurs that became trapped in mud 90 million years ago.

Fossilised skeletons of more than 25 of the bird-like animals were discovered at one site in northern China's Gobi Desert.

The creatures appear to have strayed into the boggy margins of a lake and perished as they struggled to escape.

Scientists have discovered 25 young bird-like dinosaur remains in China's Gobi Desert, thought to have died 90 million years ago after getting stuck in the mud. The skull of one the animals (R) is compared to the skull of an ostrich

Evidence suggests their legs were stuck deep into the mud, and one individual had tumbled on top of another.

The discovery sheds light on dinosaur social behaviour, indicating that juvenile individuals were left to fend for themselves when adults were preoccupied with nesting or brooding.

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'These youngsters were roaming around on their own,' said Tan Lin, from the Department of Land and Resources of Inner Mongolia, who was a member of the joint U.S.-Chinese expedition to the fossil site.

All belonged to the same species of two-legged ostrich-like dinosaur, Sinornithomimus dongi, which may have been covered with primitive feathers.

Growth rings in the bones showed they ranged in age from one to seven years.

The first bones from the herd were spotted by a Chinese geologist in 1978 at the base of a small hill in a desolate windswept region of Inner Mongolia.

University of Chicago professor Paul Sereno (R) compares fossil bones at the site of a buried dinosaur herd in the Gobi Desert of Inner Mongolia in China

Around 20 years later, a Sino-Japanese team excavated the first skeletons, naming the dinosaur Sinornithomimus (Chinese bird-mimic).

The latest find followed extensive quarrying at the site, delving deep into the base of the hill.

The skeletons were intact apart from missing hip bones, probably removed by scavengers working over the meatiest parts of the bodies shortly after the animals died.

Plunging marks in the mud surrounding the remains recorded the creatures' failed attempts to free themselves.

Professor Paul Sereno, from the University of Chicago, who co-led the expedition, said: 'These animals died a slow death in a mud trap, their flailing only serving to attract a nearby scavenger or predator.'

U.S. colleague Dr David Varricchio, from Montana State University, said: 'Finding a mired herd is exceedingly rare among living animals. The best examples are from hoofed mammals.'

He added: 'I was saddened because I knew how the animals had perished. It was a strange sensation and the only time I had felt that way at a dig.'

The discovery was reported in the journal Acta Palaeontologica Polonica.

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Stuck-osaurus: Mass grave unearthed of young dinosaurs who died 90million years ago after trapped in the mud